1. Field of the Invention
The present invention relates to a detecting system, a system interconnection generator which allows electric power generated by using sunlight, fuel cell or the like as an energy source to be superimposed on a line of a commercial electric power source, to an air conditioner which operates in cooperation with the system interconnection generator, and also to a method for calibrating physical quantities such as a voltage value and a current value, which are detected by detecting means.
2. Description of the Related Art
A separate-type air conditioner comprised of an indoor unit and an outdoor unit has the structure in which an apparatus which forms a refrigerating cycle is installed in the indoor unit and the outdoor unit in such a manner as to be properly divided into the two units, and due to evaporative and condensing action of a refrigerant circulated in a refrigerating cycle, the air conditioner is provided to achieve air conditioning for an interior of a room to be air-conditioned.
In this air conditioner, a microcomputer is provided for each of the indoor unit and the outdoor unit to effect control of operation of each of the units. Each microcomputer allows data-exchangeable interconnection by serial communication circuits and signal lines. The microcomputer provided in the indoor unit effects overall control of the air conditioner.
In recent years, a solar generator utilizing solar energy has widely spread. The solar generator converts electric power generated by sunlight to the same mode as a commercial electric power source, and thereafter, allows the converted electric power to be superimposed on a line of the commercial electric power source.
Some air conditioners allow information exchange with such solar generator, and also utilize, as one of operation information, information based on electric power (i.e., an value of power generated by a solar cell) outputted from a system interconnection generator.
On the other hand, in a case in which abnormality such as power supply interruption occurs in the commercial power source when electric power generated by a system interconnection generator is supplied as the commercial power source, it is necessary to stop supply (generation) of electric power so as to prevent a harmful influence caused by an individual operation of the system interconnection generator. For this reason, the microcomputer for controlling power generation of the system interconnection generator includes a protective function which operates based on a constant set by a dip switch, a rotary switch, or the like.
This protective function requires various parameters so as to monitor the state of a line of a commercial power source. An operator sets, by effecting input setting using a dip switch or effecting input using a rotary switch, a variable resistance, and an A/D conversion input device, a parameter based on a location where the system interconnection generator is installed or the kind of a system to be interconnected. The set parameter is converted to a corresponding signal and is stored in the microcomputer. As a result, when the state of the line of the commercial power source exceeds any parameter, the protective function becomes effective (active) to parallel off the system interconnection generator from the line of the commercial power source.
However, in order to properly monitor generated electric power and the state of the line of the commercial power source, it is necessary that items of the parameter be increased and be set finely. In order that items of the parameter be increased and be set finely, the number of ports of the microcomputer needs be increased to correspond to the number of items. Further, a setting operation becomes complicated and input of a concrete numerical value is impossible in a dip switch or the like. For this reason, it is difficult to set a proper parameter.
Moreover, the parameter varies depending on, for example, a location where the system interconnection generator is installed, and therefore, it is necessary to set a proper parameter in accordance with the location of installation, or the like. Accordingly, an operator needs to move to the location where the system interconnection generator is installed so as to alter a stored parameter.
A solar generator used as the system interconnection generator generates electric power by a solar cell. The output voltage-output current characteristic of the solar cell is generally represented by a curve as shown in FIG. 14A. Accordingly, the output voltage-output power characteristic of the solar cell is represented by a curve as shown in FIG. 14B. Namely, in the solar cell, when the output voltage is set in a range of 0[V] to a predetermined value, output power gradually increases. When the output voltage exceeds the predetermined value, output power gradually decreases. The output power at the predetermined voltage becomes the maximum power of the solar cell and the point of the maximum power is a maximum power point P.sub.m.
As control for taking out the maximum power from the solar cell having the above-described characteristic, there is known Maximum Power Point Tracking (MPPT) control which changes output power so that an operating point of the solar cell constantly tracks the maximum power point P.sub.m.
The MPPT control allows the operating point of the solar cell to approach to the maximum power point (i.e., optimum operating point) by the procedure in which a voltage command value which becomes a target value controlled by an operating voltage of the solar cell is changed slightly a fixed time interval and an output power of the solar cell at this time is measured and compared with a previously measured value, and the above-described voltage command value is changed in a direction in which output power constantly increases.
Conventionally, control of solar power generation using such MPPT control or the like is effected based on results of detection of output voltage, output current, and the like, of the solar cell in a detecting section.
However, in the above-described conventional technique, the results of detection in the detecting section is used for control of solar power generation in a state of being left unchanged, and therefore, there is a drawback in that high-accurate control cannot be effected due to an error of measurement of an object to be detected, which is mainly caused by differences of individual characteristics in the detecting section.
Concretely, when solar power generation is effected by, for example, MPPT control, the output current and output voltage of the solar cell are detected by the detecting section, and based on the results of detection, output power of the solar cell is calculated, and further, control is made so that the output power becomes maximum. However, at this time, when an error occurs in the results of detection of the output voltage and output current, high-accurate MPPT control for obtaining a proper output power becomes difficult. Meanwhile, the same may be said of, in addition to the detecting section which detects the output current and output voltage of the solar cell, a detecting section which detects output current of an inverter circuit generally used in a solar generator, the temperature of a radiating heat sink of the inverter circuit, and the like.